BONN
— ORDINARILY, the expulsion of millions of Germans from their homeland would be just another chapter in the tragic history of World War II. But with German reunification on the horizon, what was once considered the past is suddenly current and relevant. At the end of the war, 12 million Germans fled or were forced from their homeland in what are now parts of Poland, Czechoslovakia, and the Soviet Union. Their ancestors had lived there for 700 to 800 years. On their journey westward, many expellees gave up everything, including their lives.

Now, when it looks as if a united Germany will sign away all claims to these eastern lands, the expellees and their descendents in West Germany want a say in the decision.

Since there was no treaty ending World War II, the West German Constitution still considers the far-reaching, prewar borders of 1937 to be Germany's true borders. This includes about a third of present-day Poland.

But the League of Expellees, with 2 million dues-paying members, adamantly opposes an ``unconditional'' Polish border guarantee. They are claiming rights to their homeland, including the right to move back. They expect reparations for lost property and lost use of that property (to the tune of hundreds of billions of marks). They want to guarantee the rights of the 800,000 to 1 million Germans in Poland, whose culture was suppressed under the Communist regime.

When it comes to actual claims on these lands, ``the starting point of negotiations must be the 1937 borders,'' says Herbert Czaja, president of the league.

West German Chancellor Helmut Kohl has repeatedly assured Poland that no one intends to violate its border. At the same time, he says he can't negotiate a treaty because he has no legal authority to speak for a united Germany.

The international and domestic criticism for this position has been sharp. One of Mr. Kohl's own coalition partners, the popular Foreign Minister Hans-Dietrich Genscher, strongly supports the Poles on this issue. He met with Kohl over the controversy yesterday, and the issue is expected to surface again in the Bundestag later this week.

Criticism of Kohl is intense, especially since it's believed that Kohl's real concern is not the legal issue but keeping the expellees happy. In a country whose government is built on carefully balanced coalitions, even the mutiny of 2 million league members could tip the Dec. 2 national elections against Kohl.

More than 20 league members are also members of the West German parliament, or Bundestag. The league receives financial support from the federal government and prominent national leaders, including the chancellor, speak at league functions.

Consideration of the expellees was borne out Friday, when the Bonn government suddenly proposed that any future border treaty be linked to two conditions. Poland must confirm a 1953 Polish waiver to war reparations. It must also guarantee rights for the German minority in Poland, an issue that Kohl and the Polish prime minister agreed on during Kohl's state visit to Warsaw last November.

Foreign Minister Genscher's party, the Liberal Democrats, says a border treaty need not be coupled with any conditions.

Critics say many of the league's claims will have to fall. It is the price of the war; it is the price for a united Germany, they say.